The invention relates to a novel process for the preparation of 1,1,1-trifluoro-2-aminoalkanes which comprises reacting the corresponding N-alkylidene benzylamines with a primary amine whereby the product compound is removed by distillation.
1,1,1-trifluoro-2-aminoalkanes are useful as intermediates for the preparation of a variety of compounds which are useful as agrochemicals, pharmaceuticals or dyes. In particular, they are key intermediates in the preparation of insecticidal benzamides as disclosed for example by DE 36 11 193 and of fungicidal 7-(1,1,1-trifluoroalk-2-ylamino)-6-(halophenyl)-triazolopyrimidines which are described for example in WO 98/46608.
T. Ono, et al., J. Org. Chem. 61,1996, 6563-6569 disclose a method for the preparation of 1,1,1-trifluoro-2-aminopropane by rearrangement of N-(1,1,1-triflluoroisopropylidene)benzylamine to N-benzylidene-1,1,1-triflluoroisopropylamine. The resulting benzylidene compound is hydrolyzed to the amine hydrochloride with hydrochloric acid using ether as diluent. The amine hydrochloride is separated from the benzaldehyde and the free amine is prepared by action of triethylamine on the amine hydrochloride.
Thus the process known from the art requires several steps to yield the desired 1,1,1-trifluoro-2-aminoalkanes. The novel process has been found to be advantageous in producing 1,1,1-trifluoro-2-aminoalkanes in only up to two steps.